A so-called “inkjet printing apparatus” has been popular, in which heat energy corresponding to a driving pulse is applied to ink to generate bubbles by film boiling, and ink is discharged from printheads onto a print medium such as paper by generated bubbles to print an image.
In this inkjet printing apparatus, in order to maintain high-quality image printing, it is important for a user to optimally manage ink viscosity. Hence, in order to optimally manage ink viscosity, the inkjet printing apparatus has a function of monitoring a change in ink viscosity, and when ink viscosity falls outside a predetermined allowance, notifying the user of a message indicating this. Since the inkjet printing apparatus has such function, the user can take an appropriate action such as replacing an ink cartridge of a predetermined color, on the basis of this notification (as described above, output information required to take the appropriate action is generally referred to as “ink viscosity information”).
Most of conventional inkjet printing apparatuses monitor the change in ink viscosity by measuring the electrical conductivity of ink, the pressure in an ink channel, and the like (e.g., see Japanese Patent Laid-Open No. 7-178924).
However, the method of monitoring the change in ink viscosity by measuring the electrical conductivity and pressure poses the burden of cost, and increases an apparatus size, thus posing a problem. Hence, a demand has arisen for providing ink viscosity information required to take an appropriate action for ink at low cost without an increase in the apparatus size.